JP6079745B2 - Inspection method and manufacturing method of fuel cell - Google Patents

Description

  The present invention relates to a fuel cell.

  The following method is known as a method for inspecting a fuel cell including an ionomer. First, the maximum output of the fuel cell is measured during periodic inspection. When the measured value is 60% or less of the specified value, the fuel cell is subjected to heat treatment. After the heat treatment, if the maximum output is larger than 60% of the specified value, it is determined that there is no problem with continuous use. The reason for this determination is that the reason why the maximum output value was 60% or less of the specified value before the heat treatment is presumed to be swelling of the ionomer. This can be estimated because the swelling of the ionomer is recovered by heat treatment.

JP2013-122815A

  In the case of the above prior art, the inspection of the output under the transient operating condition is not considered. Based on the above-described prior art, the present invention has an object of realizing an output inspection under a transient operating condition.

  SUMMARY An advantage of some aspects of the invention is to solve the above-described problems, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a method for inspecting a fuel cell is provided. The method includes an ascending step of increasing the current density at a speed equal to or higher than a predetermined speed; a first voltage value that is a voltage value when the current density reaches a predetermined current density or higher; And a determination step of determining whether the fuel cell is normal or abnormal by comparing. According to this embodiment, it is possible to inspect transient operating conditions. This is because the determination based on the first voltage value reflects a transient operating condition. The transient operating condition is reflected because the first voltage value is a voltage value when the current density is increased at a speed equal to or higher than a predetermined speed and reaches a predetermined current density or higher.

(2) In the above aspect, the second voltage value is a cell voltage after a predetermined time has elapsed since the rising step is completed; in the determining step, the second voltage value and the first voltage value are You may determine with it being abnormal when the voltage difference which is a difference is more than a reference value. According to this embodiment, the determination can be made without taking into account variations due to individual differences in fuel cells.

(3) In the above aspect, in the determination step, when the voltage difference is equal to or greater than the reference value, it is determined that the first abnormality is present, and when the second voltage value is less than a predetermined value, the first It may be determined that the second abnormality is different from the abnormality. According to this aspect, it is possible to distinguish between the first abnormality and the second abnormality.

(4) In the above embodiment, the second voltage value is a predetermined fixed value, and the determination step determines that the first voltage value is abnormal when the first voltage value is less than the second voltage value. May be. According to this embodiment, the inspection time is shortened.

(5) In the above embodiment, the predetermined speed may be 0.5 A / (cm ² · sec).

(6) In the above embodiment, the current density when the increase is completed may be the current density at the maximum output in the usage range of the fuel cell. According to this form, it can test | inspect about the case where it becomes the maximum output.

(7) In the above embodiment, the current density before the rise starts may be 0.2 A / cm ² or less. According to this form, it can test | inspect about the case where a current density rises from 0.2 A / cm < ² > or less.

  The present invention can be realized in various forms other than the above. For example, the present invention can be realized in the form of a fuel cell manufacturing method including the above inspection method, a computer program for realizing the above inspection method, a non-temporary storage medium storing this computer program, and the like.

1 is a schematic configuration diagram of a power generation inspection system. Process drawing of an inspection process. The graph which shows a mode that a cell voltage and a current density change by test | inspection processing. The graph which shows the relationship between an output and the amount of cationic contamination per unit area. The graph which shows the voltage-current characteristic of a fuel cell. The graph which shows a mode that electric current density is raised / lowered. The graph which shows a mode that a cell voltage and a current density change (comparative example). The graph which shows a mode that a cell voltage and a current density change (comparative example).

  FIG. 1 shows a schematic configuration of a power generation inspection system 100. The power generation inspection system 100 is a system for inspecting a fuel cell stack for an automobile. The power generation inspection system 100 includes an intermediate plate 10, a cell monitor 20, and a data collection system 30. The fuel cell stack has a stack structure in which a plurality of cells FC are stacked. The cell FC includes a power generator and a separator that sandwiches the power generator. The power generator includes an MEA (membrane electrode assembly). The MEA is configured by joining a cathode electrode, an electrolyte membrane, and an anode electrode.

  The intermediate plate 10 is disposed between the cells FC. The laminated body including the plurality of cells FC and the plurality of intermediate plates 10 is fastened by applying a load in the direction indicated by the white arrow in FIG.

  The cell monitor 20 is a device that measures the cell voltage of each cell FC. The cell monitor 20 is connected to each of the plurality of intermediate plates 10 via a cell monitor cable 22.

  The data collection system 30 is connected to the cell monitor 20 via the power cable 24. The data collection system 30 acquires the cell voltage of each cell FC measured by the cell monitor 20. The data collection system 30 forms the above-described stacked body and the closed circuit 40. The data collection system 30 controls the value of current flowing through the closed circuit 40 using a built-in circuit.

  The power generation inspection system 100 includes a fuel gas supply system (not shown) for supplying hydrogen to a plurality of cells FC, an oxidant gas supply system (not shown) for supplying air to the plurality of cells FC, and a plurality of A cooling water supply system (not shown) for supplying cooling water to the intermediate plate 10 is provided. The relative humidity of the supplied air is controlled to a predetermined value. The predetermined value is a value for reproducing an operation of supplying air to the cathode without humidification (non-humidification operation).

  FIG. 2 is a process diagram of the inspection process. The inspection process is executed as part of the fuel cell manufacturing process. The inspection process is executed by the data collection system 30 in order to inspect each cell FC. In the inspection process, necessary amounts of hydrogen, air, and cooling water are supplied.

  FIG. 3 is a graph showing how the cell voltage and current density of the cell FC change due to the inspection process. Hereinafter, the inspection process will be described with reference to FIG.

First, the current density of each cell FC is controlled to a predetermined value J1 (step S110). Predetermined value J1 is the current density to achieve the produced water is less operation, in the present embodiment is any value of 0.05 A / cm ² or more 0.2 A / cm ² or less. The control of the current density is realized by controlling the current value flowing through the closed circuit 40. The calculation of the current density is realized by dividing the value of the current flowing through the closed circuit 40 by the area value of the power generation region of each cell FC. This area value is input to the data collection system 30 in advance.

Next, the current density is increased to the maximum value J2 (step S120). The maximum value J2 is a current density at the maximum output of the fuel cell, and is 2.0 A / cm ² or more and 3.0 A / cm ² or less in the present embodiment. The rising speed is set to 0.5 A / (cm ² · sec). FIG. 3 shows how the current density starts increasing from time t1, and the current density increasing ends at time t2. When the current density increases, the cell voltage decreases according to the voltage-current characteristics of the cell FC as shown in FIG.

  Subsequently, the cell voltage V3 of each cell FC is acquired after a predetermined time has elapsed after the current density reaches the maximum value J2 (time t3) (step S130). The predetermined time is an arbitrary time from 0 seconds to 10 seconds, and 5 seconds is adopted in the present embodiment.

  FIG. 3 shows how the voltage V3a is acquired in the normal case, the voltage V3b in the case of cation contamination, and V3c in the case of other abnormalities.

  Cationic contamination is a phenomenon in which sulfonic acid groups contained in an electrolyte membrane are poisoned by cations. The cation is a cation such as iron, aluminum, nickel, cerium, or cobalt. There are various causes for these cations to be mixed into the electrolyte membrane. For example, it mixes as a foreign substance in a manufacturing process, or elutes and mixes in from other members at the time of electric power generation. Iron, aluminum, and nickel may be mixed in the manufacturing process, or may be eluted from auxiliary parts and separators. Cerium and cobalt may be eluted and mixed from an antioxidant (radical quencher). When sulfonic acid groups are poisoned by cations, the resistance of proton conduction increases, and the output decreases particularly during drying.

  After step S130, the current density is maintained at the maximum value J2, and after a predetermined time has elapsed (time t4), the cell voltage V4 of each cell FC is acquired (step S140). In this embodiment, 10 minutes is adopted as the predetermined time. FIG. 3 shows how the voltage V4a is acquired in the case of normality and cation contamination, and V4c is acquired in the case of other abnormalities.

  Next, for each cell FC, it is determined whether the difference between the cell voltage V4 and the cell voltage V3 (hereinafter referred to as “voltage difference ΔV”) is less than the threshold value Vt1 (step S150). When there is a cell FC having a voltage difference ΔV equal to or greater than the threshold value Vt1 (step S150, NO), it is determined that the cell FC is a defective product in which cation contamination has occurred (step S160).

  In the case of the cation contamination described above, the voltage difference ΔV is (voltage V4a−voltage V3b), which is equal to or greater than the threshold value Vt1. On the other hand, in the normal case, the voltage difference ΔV is (voltage V4a−voltage V3a), and in other abnormal cases, the voltage difference ΔV is (voltage V4c−voltage V3c), both of which are less than the threshold value Vt1.

FIG. 4 is a graph showing the relationship between the output (W) of the fuel cell and the amount of cation contamination (μg / cm ² ) per unit area of MEA. FIG. 5 is a graph showing the voltage-current characteristics of the fuel cell. Hereinafter, the influence of cation contamination will be described using these two graphs.

The graph shown in FIG. 4 shows characteristics in a steady state and characteristics in a transient state. The constant time is a period in which the current density is controlled to be constant. The transient time is immediately after the current density is increased as described in step S120 of the inspection process. These characteristics are obtained when the current density is high (predetermined value of 1.2 A / cm ² or more).

  As shown in FIG. 4, in the steady state, the output does not decrease much even if the amount of cation contamination increases. On the other hand, when the amount of cation contamination increases in the transient state, the output is greatly reduced.

  On the other hand, the graph shown in FIG. 5 shows the characteristics in the case of an acceptable product in which the cation contamination amount is less than the reference value, and the characteristics in the case of an unacceptable product in which the cation contamination amount is greater than or equal to the reference value. In the case of a rejected product, the wet state and the dry state are shown. The wet state is a state where the amount of water contained in the electrolyte membrane constituting the MEA reaches the amount for good proton conduction. Conversely, the dry state is a state where the amount of water is less than the amount for good proton conduction.

As shown in FIG. 5, when the current density is low, there is almost no difference in any case. On the other hand, when the current density is increased, a difference gradually starts from around 1.2 A / cm ² . That is, even at the same current density, the cell voltage of the rejected product is lower than that of the acceptable product. The difference increases as the current density increases. However, the decrease in output is reduced in the wet state compared to the dry state.

  Thus, the influence of cation contamination changes depending on whether it is wet or dry because both drying and cation contamination increase the resistance of proton conduction. In other words, in the wet state, even if cation contamination occurs, the proton conductivity is not significantly deteriorated, whereas in the dry state, the proton is affected by both the cation contamination and the drying of the electrolyte membrane. The conductivity is greatly deteriorated.

  Derived from the above description described in conjunction with FIG. 4 and FIG. 5 is that the current density is high and it is easy to detect cation contamination when the cell voltage is measured in the dry state. However, if the current density is high, the amount of generated water increases and the product becomes wet. Therefore, the above measurement conditions cannot be realized simply by increasing the current density. Therefore, in the present embodiment, the above measurement conditions are realized by increasing the current density rapidly as in step S120. That is, since the amount of generated water is small in the case of a low current density, a high current density and a dry state were realized simultaneously by rapidly increasing the current density from that state.

  In the inspection process, when the voltage difference ΔV is less than the threshold value Vt1 (step S150, YES), for each cell FC, it is determined whether the cell voltage V4 is greater than or equal to the threshold value Vt4 (step S170). When there is a cell FC whose cell voltage V4 is less than the threshold value Vt4 (step S170, NO), it is determined that the cell FC is a defective product due to an abnormality other than cation contamination (step S180). The threshold value Vt4 is a threshold value experimentally determined as a voltage value to be satisfied at the maximum output.

  Thus, after continuing the steady operation that maintains the high current density, if the cell voltage does not recover, it can be determined that the product is defective due to other than cation contamination. This is because it becomes latent when the electrolyte membrane is wet.

  When there is a cell FC whose cell voltage V4 is equal to or higher than the threshold Vt4 (step S170, YES), the current density is increased or decreased as described later with reference to FIG. 6 until the transient output is stabilized (step S190). Step S190 is executed to prepare for shipment of the cell FC determined to be normal. After step S190, the cell FC determined to be normal is assembled as a fuel cell component.

  On the other hand, the cell FC determined to be abnormal in steps S160 and S180 is sent to disposal or recycling.

FIG. 6 is a graph showing how the current density changes in step S190. As shown in FIG. 6, the predetermined value J1 is maintained, the increase is 0.5 A / (cm ² · sec), the maximum value J2 is maintained, and the decrease is repeated at −0.5 A / (cm ² · sec). The transient output is a cell voltage immediately after the current density reaches the maximum value J2.

  7 and 8 are graphs for explaining a comparative example. 7 and 8 show the behavior of the cell voltage when step S120 in the inspection process is changed.

FIG. 7 shows a case where the current density is increased linearly and the increasing speed is set to 0.03 A / (cm ² · sec) in step S120. FIG. 8 shows a case where the current density is increased stepwise in step S120 and the average rate of increase is set to 0.03 A / (cm ² · sec). That is, in any case, the current density is gradually increased as compared with the embodiment.

  As shown in FIG. 7, the difference between the normal cell voltage V3a ′ at time t3 ′ and the cation-contaminated cell voltage V3b ′ is smaller than in the embodiment. Therefore, the difference in voltage difference ΔV is small between the normal case and the cation contamination case. Similarly in the case of FIG. 8, the difference between the cell voltage V3a ″ in the normal case and the cell voltage V3b ″ in the case of cation contamination is smaller than that in the embodiment. Therefore, in these methods, detection of cation contamination is difficult as compared with the embodiment.

  According to the embodiment described above, it is possible to accurately detect a decrease in output during a transient due to cation contamination. If the output at the time of transition is low, even if the driver depresses the accelerator pedal, the driver does not accelerate so much, so it is easy for the driver to recognize it as a malfunction. Therefore, it is useful to be able to accurately detect a decrease in output during a transition in the manufacturing process.

  In addition, the cause of the output fall at the time of a transition is not restricted to the cation contamination illustrated in this embodiment. That is, even if the output at the time of transition is reduced due to other causes, the output reduction can be accurately detected according to the inspection processing of this embodiment.

  The present invention is not limited to the embodiments, examples, and modifications of the present specification, and can be implemented with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in the embodiments described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects described above, replacement or combination can be performed as appropriate. If the technical feature is not described as essential in this specification, it can be deleted as appropriate. For example, the following are exemplified.

The rate of increasing the current density may not be 0.5 A / (cm ² · sec), that is, 0.5 A (cm ² · sec) or less (for example, 0.4 A / (cm ² · sec)). However, it may be 0.5 A (cm ² · sec) or more (for example, 0.6 A / (cm ² · sec)). The speed at which the current density is increased may be any speed that causes a change from an operation state at a low current density to an operation state at which the electrolyte membrane is in a dry state with a high current density.
The increase in current density may be non-linear, non-linear or stepped. In this case, the rising speed may be calculated on an average.

  The time for measuring the transient state due to the increase in current density may be before the increase in current density is completed. For example, it is considered that the difference between the acceptable product and the unacceptable product due to cation contamination can be detected even 1 second before the completion of the ascent.

  The time t3 immediately after increasing the current density may be any time as long as it is the time before the steady operation state is reached. For example, it may be after an arbitrary time (for example, 20 seconds) has elapsed since the current density reached the maximum.

  The time t4 after the elapse of a predetermined time after increasing the current density may be any time as long as the time is after the cell voltage is stabilized. For example, it may be after an arbitrary time (for example, 5 to 20 minutes) from the time when the current density is maximized.

If the cell voltage V3 immediately after the increase in the current density is less than a reference value that is predetermined as a fixed value, it may be determined as abnormal. This determination shortens the inspection time. Here, the fixed value means a value fixed so as not to be affected even if the cell voltage fluctuates in the inspection. Of course, it may be possible to instruct the data collection system to change the value as adjustment of the inspection, or a value that cannot be changed.
In the case of the above determination method, it is not necessary to distinguish between cation contamination and other abnormalities.

Instead of the voltage difference ΔV, a value obtained by dividing the cell voltage V4 (cell voltage during steady state) by the cell voltage V3 may be compared with a reference value, and if the value is equal to or greater than the reference value, it may be determined that there is an abnormality.
The predetermined value J1 and the maximum value J2 of the current density may be arbitrary values.

The fuel cell to be inspected may not be for automobiles but may have a current density that suddenly increases during use. For example, it may be mounted on other transportation equipment (train, ship, etc.).
You may perform the test | inspection of this application as a test | inspection after shipping. For example, it may be executed as a periodic inspection.

DESCRIPTION OF SYMBOLS 10 ... Intermediate plate 20 ... Cell monitor 22 ... Cell monitor cable 24 ... Power cable 30 ... Data collection system 40 ... Closed circuit 100 ... Power generation inspection system

Claims (7)

A method for inspecting a fuel cell,
An ascending process for increasing the current density at a speed equal to or higher than a predetermined speed;
It is determined whether the fuel cell is normal or abnormal by comparing a first voltage value, which is a voltage value when the current density reaches a predetermined current density or more, by the ascending step with a second voltage value that is a criterion. look including a determination step of,
The second voltage value is a cell voltage after a predetermined time has elapsed since the rising step is completed,
In the determination step, when a voltage difference that is a difference between the second voltage value and the first voltage value is greater than or equal to a reference value, it is determined as a first abnormality, and the second voltage value is less than a predetermined value. In this case, it is determined that the second abnormality is different from the first abnormality. A method for inspecting a fuel cell,
An ascending process for increasing the current density at a speed equal to or higher than a predetermined speed;
It is determined whether the fuel cell is normal or abnormal by comparing a first voltage value, which is a voltage value when the current density reaches a predetermined current density or more, by the ascending step with a second voltage value that is a criterion. look including a determination step of,
The current density at the time when the rising step is completed is a current density at the maximum output in the usage range of the fuel cell. A method for inspecting a fuel cell,
An ascending process for increasing the current density at a speed equal to or higher than a predetermined speed;
It is determined whether the fuel cell is normal or abnormal by comparing a first voltage value, which is a voltage value when the current density reaches a predetermined current density or more, by the ascending step with a second voltage value that is a criterion. look including a determination step of,
The current density before the rising step is started is 0.2 A / cm ² or less. A method for inspecting a fuel cell,
An ascending process for increasing the current density at a speed equal to or higher than a predetermined speed;
It is determined whether the fuel cell is normal or abnormal by comparing a first voltage value, which is a voltage value when the current density reaches a predetermined current density or more, by the ascending step with a second voltage value that is a criterion. look including a determination step of,
The second voltage value is a predetermined fixed value,
In the determining step, when the first voltage value is less than the second voltage value, it is determined as abnormal. The inspection method according to any one of claims 1 to 4, wherein the predetermined speed is 0.5 A / (cm ² · sec). A fuel cell manufacturing method comprising:
The manufactured cell is inspected by the inspection method according to any one of claims 1 to 5 ,
A manufacturing method for manufacturing a fuel cell using a cell that has passed the inspection. A fuel cell manufacturing method comprising:
An ascending process for increasing the current density at a speed equal to or higher than a predetermined speed;
It is determined whether the fuel cell is normal or abnormal by comparing a first voltage value, which is a voltage value when the current density reaches a predetermined current density or more, by the ascending step with a second voltage value that is a criterion. Judgment process to
A step of manufacturing a fuel cell using the cells determined to be normal ;
Manufacturing method, comprising.

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